Today, we have more delicious calories available than ever before and more technology to do what our muscles used to do. Thanks to radical changes in our environment, our natural traits have put us at risk for obesity. Placing humans in this modern setting of fast-food restaurants, vending machines, elevators, and video games is like dropping a polar bear into the Sahara Desert, according to Katz. We are no more adapted to the modern world than the polar bear is to the desert. Just as polar bears would overheat in the Sahara Desert, we overeat in a sea of calories in the modern world.

Diets rich in fruits, vegetables, and whole grains, restricted in animal fats and trans fat from processed foods, limited in refined starches and sugar, providing protein principally from lean sources, and offering fat principally from monounsaturated and polyunsaturated oils are linked to good health. In addition, the role of physical activity in weight loss is quite convincing.